This proposal aims to identify neuropsychological processes associated with social cognition in primates through a comprehensive comparison of the cognitive, behavioral and neuroanaomical substrates underlying face recognition and emotional processing, in two species closely related to humans, chimpanzees and rhesus monkeys. Providing a detailed comparison of cognitive and emotional processes in rhesus and chimpanzees will serve the long-term objective of helping to identify the best species to model some aspects of human behavior. These questions are critically important because of the numerous psychiatric, neurodegenerative, and developmental disorders present in humans that share face recognition and emotional processing impairments as part of their primary phenotype. Some aspects of face recognition and garnering emotional information from facial expressions are impaired in individuals with autism, schizophrenia, psychopathy, prosopagnosia, Fragile X, Alzheimer's, William's syndrome, major depression, and various forms of dementia. This project proposes five specific aims. Specific Aim 1 will examine what features monkeys and apes use to discriminate faces, including eye gaze, spatial orientation, facial features, and individual familiarity. Specific Aims 2 and 3 will examine the role of auditory and visual cues in individual recognition and the categorization of facial expressions. Specific Aim 4 will examine the ability of monkeys and apes to recognize kin relationships using the faces of unfamiliar individuals, and whether the heritability of physiognomic characteristics differers with maternal or paternal influences. Finally, integrating several of these questions is Specific Aim 5 that will compare patterns of regional cerebral glucose metabolism during face and facial expression processing using 18F-FDG positron emission tomography. The proposed studies go beyond previous studies on nonhuman primates in that they aim to compare social cognition processes in two different primate species that vary in their social organization, genetic similarity to humans, and cognitive abilities. Moreover, by using similar training and testing methodologies our work will extend these cognitive findings to comparisons of the patterns of neural specificity using functional neuroimaging.